Hyatt.] 120 [April S. 
oeneral application as the term "tribe" used by iiiaiiy naturalists 
for associating related genera in a subfamily, and for obvious 
reasons it is perhaps better to abandon the word "branch" as used 
in this way for the more commonly used term "tribe" and transfer 
"brancli"to the suborder. 
In working upwards the next main subdivision is of course the 
family. The family in terms of bioplastology, as shown in my 
former publications, is an assemblage of genera or series arising 
from a common radical stock. 
The application of a descriptive term to a suborder is of equal 
importance to that of the family. This is also, together with 
the order and class, one of the terms which according to Professor 
Blake ap[)lies only to associations of contemporaneous forms. I 
presuuie that this idea is founded wholly upon the original use of 
these terms among living organisms, I)ut they were found to be 
equall}^ applicable in paleontology when research begau in this 
branch of science and have become established in the literature. 
r do not consequently understand why they cannot take the next 
step and be etjually convenient and significant in bioplastology. 
Their artilicial meaning as translated by many naturalists is 
certainly a serious ol)jection, but the next generation is not likely 
to have the same restricted views, and any attempt to disturb 
terms so elastic as these and so well established in the literature of 
natural science will do more harm than good. 
The suborder among fossil cephalopods is a remarkably signifi- 
cant group in the evolution of the orders and serves to show us 
the larger cycles in time by which this is accomplished, as well as 
the decisive steps which occur in the progressive history of the 
structures and organs. The phyloparagerontic and terminal forms 
of genera of these suborders are often also excessively degraded. 
Thus, the Goniatitinae, Cl3'meniae, Arcestinae, Ceratitinae, Lyto- 
ceratinae, and Ammonitinae form a gi'and structural series of steps 
in the evolution of the order of ammonoids, and each one is a 
definite advance in progression. At the same time they liave 
within their own limits highly degraded forms such as occur in 
Ceratitinae in the uncoiled Choristoceras, the turritelloid shell 
Cochlioceras, and the straight.cone of Rhabdoceras. It is not at 
all unlikely that similar extreme cases may be eventually found in 
the other suborders since similar phyloparagerontic forms are also 
found in Ammonitinae and Lytoceratinae. They are distinct 
